Review Articles

Kraft pulp and paper mills have several advantages for serving the emerging biorefinery industry as a source of raw materials. This review examines technologies for producing liquid biofuels, chemicals, and advanced materials from woody feedstocks to generate new sources of revenue. Market pull comes in part from government policies that drive substitution of petroleum-based products with biobased equivalents. Kraft mills have ample networks to supply feedstocks, whether these are forest residues or byproduct side streams. Pulp mills are well suited to expand sufficiently to accommodate production of value added platform chemicals that are in demand because of brand owner sustainability commitments.

Microbially derived alkanes and their derivatives are recognized as promising alternatives to petroleum-based fuels and chemicals. We review recent developments in their production, assess progress, and their potential against conventional bioethanol fermentation pathways. The success rate of genetic engineering efforts and their commercialization prospects are assessed, as well as challenges for producing fuels and chemicals from lignocellulosic biomass. Although significant progress has been made in the genetic engineering of microbes used in the production of long-chain hydrocarbons and their derivatives, titer and yield of these biomolecules are currently too low to compete with petroleum-derived products. As for microbially derived isoprenoids or fatty acids, the inherent complexity of micro-organism development will continue to present formidable challenges, making it highly unlikely of any short-term commercial take off. Nonetheless, first generation bioethanol (starch/sugar based) production is commercially established and therefore continued advancements in chemical synthesis should enable broad-scale use of bio-ethanol as a chemical feedstock for the production of advanced biofuels including butanol and other long-chain hydrocarbons.

Lactic acid is a naturally occurring organic acid that can be used in a wide variety of industries, such as the cosmetic, pharmaceutical, chemical, food, and, most recently, the medical industries. It can be made by the fermentation of sugars obtained from renewable resources, which means that it is an eco-friendly product that has attracted a lot of attention in recent years. In 2010, the U.S. Department of Energy issued a report that listed lactic acid as a potential building block for the future. Bearing the importance of lactic acid in mind, this review summarizes information about lactic acid properties and applications, as well as its production and purification processes.

Deacidification refers to chemical treatments meant to slow down the acid hydrolysis and embrittlement of books and paper documents that had been printed on acidic paper. From the early 1800s up to about 1990, papermakers used aluminum sulfate, an acidic compound, in most printing papers. Certain deacidification methods use non-aqueous media to distribute alkaline mineral particles such as MgO within the pages of the treated books. Evidence is considered here as to whether or not the proximity of alkaline particles within such documents is sufficient to neutralize the acidic species present. Because much evidence suggests incomplete neutralization, a second focus concerns what to do next in cases where books already have been treated with a non-aqueous dispersion system. Based on the literature, the neutralization of acidic species within such paper can be completed by partial moistening, by high humidity and pressure, by water condensation, as well as by optional treatments to enhance paper strength and a final drying step.

Significant developments in the area of wood modification have been achieved during the last three decades. These developments can be attributed to increased environmental concerns, the escalating demand for a high and constant quality of wood products, and the rising prices of the durable tropical timber as well as its very limited availability, as affected by illegal logging. As a consequence, a number of wood modification techniques such as chemical and impregnation modifications or heat treatments have been introduced, and some of these technologies have reached the industrial level. This review paper deals with two successful technologies, that is, wood acetylation and wood furfurylation. It briefly discusses the advantages of the new modified products and presents in short their improved properties. Published findings indicate that chemical modification of wood, to a full or partial degree, by means of acetylation or furfurylation, offers a way to transform low durability wood species to new ‘green’ wood materials having advanced qualities and properties.

This literature review aims to provide a systematic analysis of studies on the financial aspects of producing torrefied biomass and torrefied pellets. There are substantial differences in the specific technologies, operating conditions, scale of the demonstration, and properties of biomass feedstock. There is a lack of reports that consider the entire supply chain, which is required for an understanding of the high-cost steps. To obtain a robust view of the torrefaction processes’ financial prospects the authors have used both peer-reviewed and non-peer-reviewed papers that allowed the researchers to include thirty-one papers in this analysis. All these studies establish that the prices of the biomass and the final torrefied product are critical. The product yield and caloric content, which are related to pricing, were also key financial drivers. The lower freight costs due to high-energy density of the torrefied pellets was recognized and calculated, but some other benefits were not quantified. There is a need for a detailed and flexible torrefaction financial model that includes variations in financial assumptions and biomass properties. Given the uncertainty around many specific steps, there is value in including stochastic tools in these financial analyses.

Lactic acid is an important platform chemical with a wide range of applications. Production of lactic acid by fermentation is advantageous because renewable and low cost raw materials can be used as substrates. After fermentation, the broth needs to be purified to obtain pure lactic acid for further uses. Thus, efficient downstream processes are very important because they account for 50% of the production costs. This review discusses different processes that are currently employed for lactic acid recovery, focusing on precipitation, solvent extraction, and separation with membranes. Advances in such recovery processes and drawbacks that limit the application of these technologies at the industrial level are also presented.